ISL6580CR Intersil, ISL6580CR Datasheet - Page 20

• Manufacturer Part Number: ISL6580CR
• Description: IC DRIVER HIGH SIDE FET 56-QFN
• Manufacturer: Intersil
• Type: High Side/Low Side Driverr

Specifications of ISL6580CR

• Input Type: Non-Inverting
• Number Of Outputs: 12
• On-state Resistance: 20 mOhm
• Current - Output / Channel: 25A
• Current - Peak Output: 35A
• Voltage - Supply: 5 V ~ 12 V
• Operating Temperature: 0°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 56-VQFN
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

is shut down until OUT_EN or power to the ISL6590 is
cycled. The threshold has hysteresis to eliminate oscillation.
When V
high. As V
the status bit is set to 0 and a hysteresis switch sets the
IUVP threshold to 7.6V (nominal). The converter will operate
until V
complete specs). The thresholds are referenced to V
(3.3V) and vary in proportion to V
Power On Reset
The ISL6590 controller performs a Power On Reset function
internally. It holds all internal logic in a reset state until V
(3.3V) exceeds a threshold. While in the reset state all PWM
and NDRIVE signals are held at ground and all MOSFETs
are OFF.
Duty Cycle Limit
The ISL6590 limits the on time of the upper FETs. The
system designer can set the maximum ON time with the user
interface software. The value is entered as a percentage. If
the duty cycle reaches this percentage, the top side FET
turns off until the next cycle.
Component Selection and System
Flexibility
Inductor Selection System Effects
There are three major system impacts that the phase
inductance value impacts. These are transient response,
size, and efficiency.
TRANSIENT RESPONSE
Selection of higher phase switching frequency enables
selection of lower inductance values because peak current
limit protection will not be tripped with the shorter on time.
Lower inductance values can yield higher di/dt slopes to the
load in the ATR (Active Transient Response) mode of
operation in a multiphase system. ATR forces all phases to
an ON state at a given point in time producing the following
di/dt through the power stage.
This di/dt is the power stage current slope capability not the
overall system di/dt which is dependent on many other
factors including output capacitance and parasitics.
---- -
dt
di
=
FIGURE 31. INPUT UNDER VOLTAGE PROTECTION
(Vo-Vout)Phases
-------------------------------------------- -
CC
CC
falls below 7.6V (see the ISL6580 data sheet for
CC
is low (below 7V), a bit in the status register is set
L
rises from a low value to above 9.1V (nominal)
20
DD
.
DD
(EQ. 3)
DD
ISL6580
SIZE
In general lower inductance values yield smaller designs for
a given current level.
EFFICIENCY
The output inductor can be a significant contributor to
system loss. The inductance value will force a trade for
system efficiency vs. size and transient response. That is,
Physically larger, lower frequency designs will be more
efficient and produce slower transient response in the
system.
These three system criteria must be considered when
selecting or designing the appropriate inductor in a given
application.
Inductance selection
The following formulas apply to this section in selecting the
appropriate inductance for a given application:
F
T
V
V
L = inductance
D = duty cycle
T
T
Phases = number of system phases
Saturation Current
The selection process should start with average and peak-
to-peak requirements. At maximum load current the peak
current should be maintained to <25A to stay within ratings.
of the ISL6580.
S
P
ON
OFF
IN
OUT
FIGURE 32. AFFECT OF INDUCTANCE ON PEAK CURRENT
0
= single phase switching frequency
= switching period
= input voltage
= on time
∆I
= off time
= output voltage
Ipeak
Ton
INDUCTOR CURRENT
Iave
Higher Inductance
Lower Inductance
Toff